This invention relates to a bending device used, for example, in an endoscope.
As is well known, an endoscope comprises a hollow body, a flexible insertion portion extending from a front end of this body, and a flexible bending portion extending from the distal end of the insertion portion. The bending portion has a tip member at its distal end. An inspection window and an illumination window are formed at the tip member. A manipulation member for remotely controlling the bending portion is provided at the body.
A bending device serving as an internal structure of the bending portion comprises a bendable frame of a cylindrical shape, the tip member provided forwardly of the frame, a connecting tube interconnecting the frame and the tip member, and operating wires. The frame comprises, for example, a number of juxtaposed rings rotatably connected to one another. The rear end portion of the operating wire is connected to the manipulation member, and the front end portion of the operating wire is connected to the connecting tube. With this arrangement, when the manipulation member is operated, an operating force is transmitted to the connecting tube via the operating wire to bend the frame so as to direct the inspection window and the illumination window of the tip member in a desired direction.
Conventionally, as shown in FIG. 1 of Japanese Laid-Open Utility Model Application No. 50-81696, the front end portion of the operating wire has been connected to the inner peripheral surface of the connecting tube by brazing or the like. In this case, however, the connecting position is not accurate, and the connecting strength is low. Further, the operating efficiency with respect to the brazing of the front end portion of the operating wire to the inner peripheral surface of the connecting tube is very low.
Therefore, Japanese Laid-Open Utility Model Application No. 55-143806 proposes an improvement in the connection of a front end portion of an operating wire. More specifically, a rear end portion of a connecting tube is deformed by pressing to be projected inwardly so as to form a mounting portion (designated by reference numeral 6 in FIGS. 3 to 5 of this publication), and the operating wire is inserted into this mounting portion, and is fixedly secured thereto by brazing or the like. In this case, the position of connection of the front end portion of the operating wire to the connecting tube is accurate, and the connecting strength is high. Further, since the operation of fixing the operating wire to the connecting tube can be done outside of the connecting tube, the operating efficiency with respect to the brazing or the like is high.
However, in the connecting method of the above Japanese Laid-Open Utility Model Application No. 55-143806, since the mounting portion is projected inwardly of the connecting tube, the internal space of the connecting tube through which optical fibers and etc., are passed is reduced. Therefore, to compensate for the loss of the internal space due to the provision of the mounting portion, the outer diameter of the connecting tube must be increased. This makes it difficult to meet the demand that the insertion portion and the bending portion should be reduced in diameter, and correspondingly the diameter of the connecting tube should be as small as possible, as in an endoscope for inspecting the interior of the bronchus. Further, the pressing operation can not be applied to the continuous tube of a small diameter, the reduction of the diameter of the connecting tube is limited.
Japanese Laid-Open Utility Model Application No. 63-79901 discloses an interesting manner of connection of a front end portion of an operating wire. More specifically, an axial groove 13 is formed in an outer peripheral surface of a rear end portion of a tip member 1. The front end portion of the operating wire 10 is received in this groove, and in this condition a connecting tube 7 is fitted on the rear end portion of the tip member, thereby connecting the front end portion of the operating wire to the tip member. In this case, the position of connection of the front end portion of the operating wire is accurate, and there is no need to increase the diameter of the connecting tube. However, as described above, in the case of the endoscope having the narrow insertion portion and bending portion, the operating wire is very thin, and therefore it is not easy to form the narrow groove, corresponding to such a thin operating wire, in the outer peripheral surface of the tip member, and to achieve this, an expensive machine is needed.
Reference is made to other prior art related to the present invention. Japanese Laid-Open Utility Model Application No. 55-10605 describes in FIG. 1 a bending device for an endoscope. This bending device comprises a single coil serving as a cylindrical frame, and a resilient thin plate. A series of juxtaposed engagement recesses are formed in each of the opposite side edges of the resilient thin plate in the longitudinal direction of this resilient thin plate, and a series of turn portions of the coil are engaged in the engagement recesses.
U.S. Pat. No. 4,686,963 discloses a bending device for an endoscope which comprises a series of rings jointly constituting a cylindrical frame, and a resilient thin plate. A pair of axial grooves are formed respectively in diametrically-opposite portions of the inner peripheral surface of each ring, and the opposite side edges of the resilient thin plate are received in the pair of grooves in each ring. A pair of grooves are also formed in diametrically-opposite portions of an inner peripheral surface of a tip member, and the opposite side edges of the front end portion of the resilient thin plate are received in these grooves, respectively, and the resilient thin plate is connected at its front end portion to the tip member against axial movement.